A vehicle transmission receives input torque from a prime mover, typically an engine or an electric machine, and transmits an output torque to a set of drive wheels through a range of output speeds. In an automatic transmission, a hydrodynamic torque converter or an input clutch couples an engine output shaft to a transmission input member. Such a transmission may include various planetary gear sets and hydraulically-actuated clutches, with the various gear elements of the planetary gear sets interconnected to each other via different clutch combinations. In contrast, a dual-clutch transmission or DCT has two input clutches arranged on different input shafts and operable for selecting the respective oddly-numbered and evenly-numbered gear sets. In both transmission configurations, a transmission control module executes clutch shift logic to control clutch application sequencing for achieving a requested shift progression.
Transmissions may be monitored in control logic for certain types of fault conditions, e.g., clutch tie-up and engine overspeed conditions. As is well known in the art, the term “tie-up” refers to a condition in which the transmission is simultaneously in two different gear states. Shift events in an automatic transmission are ordinarily tied-up to some extent over a transient period as clutch torque capacity is removed from an offgoing clutch and increased for an oncoming clutch, and therefore all tie-up conditions are not problematic. However, if a tie-up condition persists for an extended period of time, or if clutch torque capacities of the various clutches involved in transferring or holding torque are maintained at or above a calibrated threshold torque capacity, execution of a control action may be required in order to help protect the hardware of the transmission. Engine overspeed fault conditions may result from shifts between certain gears when the resultant engine speed exceeds a level required for a commanded gear. Conventional responses to such fault conditions may be less than optimal in terms of powertrain performance, as many such actions result in disabling or severe curtailing of available drive functions.